Writing instrument



FIG. 1 is a front perspective view of a writing instrument showing my new design;

FIG. 2 is an exploded front perspective view thereof;

FIG. 3 is a right side view thereof, the left side view being a mirror image of the right side view; and,

FIG. 4 is a front view thereof.

The broken lines shown in the figures are included for the purpose of illustrating environmental structure and form no part of the claimed design. 

CLAIM The ornamental design for a writing instrument, as shown and described. 